Context: To find out the suitable factors for raising the coverage of immunization. Aims : To determine the coverage and to identify the various factors of primary immunization. Settings and Design : Urban slums of Lucknow district. Methods and Material : WHO 30-cluster sampling technique was used for the selection of the subjects. Mother, father or relative of a total of 510 children with 17 children per cluster were interviewed in the study. Statistical Analysis : Chi-square test, binary logistic regression and multinomial logistic regression analysis were done to test the statistical significance of the association. Results: About 44% of the children studied were fully immunized. Multinomial logistic regression analysis revealed that an illiterate mother (OR=4.0), Muslim religion (OR=2.5), scheduled caste or tribes (OR=2.3) and higher birth order (OR˜2) were significant independent predictors of the partial immunized status of the child; while those associated with the unimmunized status of the child were low socioeconomic status (OR=10.8), Muslim religion (OR=4.3), higher birth order (OR=4.3), home delivery (OR=3.6) and belonging to a joint family (OR=2.1). Conclusions: The status of complete immunization is about half of what was proposed to be achieved under the Universal Immunization Program. This emphasizes the imperative need for urgent intervention to address the issues of both dropout and lack of access, which are mainly responsible for partial immunization and nonimmunization respectively.